Apparatus for manufacturing a needle-rib heat-exchanger construction

ABSTRACT

An apparatus for manufacturing a needle-rib heat-exchanger construction including a band which is wound around a tube. Initially, cuts are formed on both sides of an elongate band and thereafter the band is passed through a series of engaging former wheels. A bottom part is formed into the band and top portions of the band are folded onto the bottom part. Needle-shaped ribs are formed to project from the top portions and are placed at an angle in relation to one another. The band with needle-shaped ribs is then mounted on the tube.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus formanufacturing a ribbed heat-exchanger tube and more particularly to amethod and apparatus for manufacturing a needle rib which is mounted toa heat exchanger tube.

BACKGROUND OF THE INVENTION

In the prior art, various lamellar heat exchangers are known whose heattransfer properties are not optimal in view of the efficiency of heattransfer. Various heat transfer devices consisting of needle-shaped ribsare also known, in which the heat transfer capacity is considerablyhigher than in ordinary lamellar heat exchangers.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improvedapparatus for manufacturing a ribbed heat-exchanger tube in which theheat transfer properties are optimal in view of the efficiency of heattransfer.

It is another object of the present invention to provide a new andimproved apparatus for manufacturing a needle-rib heat exchanger havingan efficiency which is maximal in view of the transfer of heat.

Accordingly, the needle-rib heat exchanger manufactured by means of theapparatus in accordance with the invention is made of a band or stripwhich is wound around a tube that transfers the heat-exchanger medium,i.e., the medium passes through an interior of the tube. In theapparatus, the band is first punched and then is guided via a number offormer wheels or roller wheels to form needle-shaped heat transfer ribs.In the punching operation, cuts are made in the sides of the band atmutual distances determined by the width of the needle ribs. After this,the band is passed via the roller wheels which shape the punched band.On completion of the shaping, the heat transfer band in accordance withthe invention comprises a sectional form in which there is a bottomportion and top portions that have been folded onto the bottom portion.From the top portions, rows of needle ribs project so that, in relationto the central axis (Y-axis) of the cross-section of the band, an acuteangle is formed between the opposite ribs, the acute angle beingfavorably about 20°.

More particularly, in the apparatus, after the rib cuts have been made,the band is shaped in five stages. In the first shaping stage A, arounding is formed into the cross-section of the band into its middlearea, and after that, in stage B, two folds are rolled to both sides ofthe roundings. After stage B, the sides of the band are raised by meansof the forming wheels in stages C and D. In the last stage E, theultimate shape of the band is obtained, in which the top sides of theband have been pressed to the vicinity of one another from the outerfolds that were formed in the stage B. Then, the needle ribs have beenraised to the ultimate position. In the last stage E, the band is shapedby means of roller wheels on which the inner sides of the roller wheels,which are placed facing one another, are at an angle in relation to oneanother. The angle is in the range of from about 55° to about 65°. Thetip angle B of the tips of the last roller wheels is acute, being in therange of from about 50° to about 60°. The tip of the roller wheel isplaced along the fold formed in the band, in which case the opposite ribparts are placed in their precise ultimate positions, in which the anglebetween the rib portions is favorably about 20°. After this, the band iswound directly, upon application of an adhesive by means of anapplicator wheel, around the tube intended for the transfer of the heattransfer medium or fluid. The tube is rotated and moved in itslongitudinal direction during winding of the band thereon.

The apparatus in accordance with the invention comprises several pairsof roller wheels which are operated by means of a closed belt loop thatis in motively coupled to an output drive shaft of a drive motor and inengagement with a drive pulley fitted on the shaft.

The method in accordance with the invention for the manufacture of aneedle-rib heat exchanger is mainly characterized in that, in themethod,

cuts are formed to both sides of an elongate band; and

the band is passed via sets, e.g., pairs, of nip-defining former wheelsin which connection a bottom part is formed into the band, and topportions are folded onto the bottom part, out of which top portionsneedle-shaped ribs project, being placed at an angle in relation to oneanother.

The apparatus in accordance with the invention for the manufacture of aneedle-rib heat exchanger is mainly characterized in that it comprises

several sets, e.g., pairs, of nip-defining former wheels which aredriven by a motor and by whose means the band is shaped before it iswound onto the tube;

a device for making cuts in both lateral sides of the band before theband is shaped by the former wheels; and

a device by whose means the tube is rotated and fed forward, in whichconnection the ready-shaped band is wound onto the tube.

More particularly, the apparatus for manufacturing a needle-ribheat-exchanger construction in accordance with the invention comprisesan elongate tube and a band wound onto the tube. The band has a centralportion and a lateral portion on each side of the central portion. Theapparatus comprises cutting means for cutting the lateral portions ofthe band, a set of former wheels for shaping the cut band, firstrotation means for rotating the former wheels, and second rotation meansfor rotating the tube and moving the tube in the longitudinal directionwhereby the band is guided through the rotating former wheels and woundonto the tube. The band is shaped by the former wheels to include abottom part, opposed top portions and needle-shaped ribs projecting froma respective one of the top portions and situated at an angle inrelation to one another.

The invention will be described in the following with reference to somepreferred embodiments of the invention illustrated in the figures in theaccompanying drawings. However, the invention is not confined to theseembodiments alone.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of embodiments of the inventionand are not meant to limit the scope of the invention as encompassed bythe claims.

FIG. 1A is a perspective view of a needle-rib heat exchanger tube.

FIG. 1B is a partial sectional view taken along line I--I in FIG. 1A.

FIG. 2A is a perspective view of an apparatus in accordance with theinvention.

FIG. 2B is a sectional view taken along line II--II in FIG. 2A.

FIG. 2C is a side view of a punching device by whose means cuts are madeinto the sides of the band in order to form the ribs.

FIG. 2D shows a perspective view of the punching tool by whose means thecuts are formed as the punching tool strikes a back-up blade and as theband is passed between the striking tool and the back-up blade.

FIG. 2E is a perspective view of part of the band as it appears afterthe punching operation.

FIGS. 3A, 3B, 3C, 3D and 3E are cross-sectional views illustrating theshaping of the ribbed band step by step by means of pairs of rollerwheels into its ultimate form, in which the band structure comprises across-sectional form in which there is a base portion, a top portionplaced above the base portion, and ribs, so-called needle ribs,projecting from the top portions in opposite directions.

FIG. 4 is a view of the former wheels which perform the step of FIG. 3E.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the accompanying drawings wherein the same referencenumerals refer to the same or similar elements, FIG. 1A is a perspectiveview of a heat-exchanger tube construction manufactured by means of theapparatus in accordance with the invention and by the method inaccordance with the invention. The heat-exchanger rib-tube constructioncomprises a central tube 10 and a band 11 which has been wound and gluedonto the tube and which comprises needle ribs 11c'₁, 11c'₂, 11c'₃ . . .A heat exchanger medium is operatively transferred through the interiorof the tube 10.

As shown in more detail in FIG. 1B, the tube 10 which transfers the heatexchanger medium comprises the band 11 wound around the tube. Band 11has a cross-sectional form in which there is a bottom or base portion11a. On the bottom portion 11a, top portions 11b₁ and 11b₂ extend andneedle-shaped ribs 11c₁ and 11c'₁ project from the top portions 11b₁ and11b₂, respectively. The opposite ribs are placed at an acute angle α inrelation to one another, the angle α being favorably about 20°. Thecross-sectional form thus defines folds t₂ and t₃. The top portions 11b₁and 11b₂ are thus inner segments of the lateral portions of the band 11while the needle-shaped ribs 11c₁ and 11c'₁ are outer segments of thelateral portions of the band 11.

FIG. 2A is a side view of an apparatus in accordance with the inventionfor the manufacture of a heat-exchanger needle-rib construction. In theapparatus, sets of nip-defining former wheels 14-18 are mounted on aframe R, and at least one wheel in each set of wheels is driven by abelt (not shown). The band 11 is wound onto the tube 10 after it haspassed through the last set of former wheels 18a₁,18a₂,18a₃ or rollerwheels and after a glue applicator wheel 19 in an associated gluingdevice 13.

FIG. 2B is a sectional view of the apparatus taken along line II--II inFIG. 2A. A drive belt H is passed from the output shaft of a motor M₁over guide pulleys a₁,a₂ . . . to drive pulleys b₁,b₂ . . . operativelycoupled to the driven roller wheel of each set of roller wheels 14-18.The same belt H is passed onto a driven rotation disc or wheel C₃ onwhich the tube 10 rests. Two upper discs or wheels C₁,C₂ are placed atan angle in relation to one another. The central shafts of the discs C₁and C₂ are placed obliquely in relation to one another so that a forwardfeed movement of the tube 10 is produced upon rotation of tube 10. Thetube 10 is rotated by means of the driven wheel C₃.

A punching device 12 is operated by means of a separate motor M₂ by theintermediate of a belt H₂. The belt H₂ is in engagement with a shaft 23which is connected with an eccentric shaft 23' which displaces the blade21 relative to the band 11 (FIG. 2C as represented by arrow L₃).

In the first stage of manufacture, the punching device 12 punches theband 11 so as to form cuts e₁,e₁ ',e₂,e₂ ' . . . on both sides of theband 11 as shown in FIG. 2E. After this, the band 11 is passedsequentially via the former wheels 14-18 to be shaped thereby and thenonto the applicator wheel 19 of the gluing device 13, and finally,having been brought to its finished form, the band is wound onto thetube 10 as the tube 10 rotates and advances.

FIG. 2C is a side view of the punching device 12 that makes the lateralcuts in the band 11. The punching device includes cooperating punchingblades 20,21. The band 11 is passed between punching blades 20,21 of thepunching device 12 that make the lateral cuts e₁,e₁ ';e₂,e₂ ', . . . inthe band 11. The punching blades comprise a lower mobile blade 20 and anupper stationary blade 21 as shown in FIG. 2D.

During operation, the shaft 23 is rotated by motor M₂ so that theeccentric cam or shaft 23' connected with the shaft 23 displaces theframe R₂ in the direction indicated by the arrow L₃ (FIG. 2C). The upperblade 21 performs the punching movement against the lower blade 20. Theupper blade 21 is mounted by means of a glide bearing G so as to obtainprecise guiding of the upper blade 21 in relation to the lower blade 20(FIG. 2A). In the middle of the mobile upper blade 21, there is a spaceE positioned so that the blade 21 cuts just at both sides, i.e., formscuts e₁,e₁ ',e₂,e₂ ',e₃,e₃ ' . . . at the two sides of the band 11, andallows the middle area of the band 11 to remain uncut to provide forcontinuity of the band 11.

FIG. 2D is a perspective view of the relative positions of the mobileblade 21 and the stationary blade 20. As shown in FIG. 2D, in its middlearea, the mobile blade 21 comprises the recessed or free space E wherebythe blade 21 cuts at both of its sides only, thus making cuts into theband 11 at both sides of the band.

FIG. 2E shows a finished cut band 11 which comprises lateral cutse₁,e'₁,e₂,e'₂,e3,e'₃ . . . at both sides of the longitudinal axis X ofthe band. The middle area of the band 11 is free from cuts (in view ofthe particular shape of the blade 21). Ribs 11c₁,11c₁ ',11c₂,11c₂ ' . .. are thus able to be formed between the cuts.

In the forming stages illustrated in FIGS. 3A-3E, for the sake clarity,the band 11 is shown with diagonal shading and, for the sake of clarityof the illustration, the related nip-defining roller wheels are shownspaced apart by a small distance. FIGS. 3A-3E illustrate the differentforming stages of the ribbed band 11 in accordance with the invention.

In the stage shown in FIG. 3A, the band is stretched in the middle areaby former wheels 14, of which one wheel 14a₁ comprises a groove and theother wheel 14a₂ comprises a central projection of corresponding shapeprotruding from the wheel face. The groove on the wheel 14a₁ is denotedby D₁, and the projection on the wheel 14a₂ is denoted by D₂ and theyare complementary to one another. By means of the wheels 14, the band 11is stretched in the middle area of the band 11, and a rounding t₁ isformed therein.

By means of the former wheels 15a₁ and 15a₂ shown in FIG. 3B, bends orfolds t₂ and t₃ are formed into the band 11 at both sides of its centralaxis X and at both sides of the stretched middle area of the band 11obtained by passage of the band 11 through wheels 14. The wheel 15a₁comprises a central arcuate groove 15b₁ and arcuate projections 15b₂ and15b₃ projecting from the wheel face at both sides of the central axis ofthe wheel. In a corresponding manner, the wheel 15a₂ comprises grooves15b₂ ', 15b₃ ' jointly operative with the projections 15b₂ and 15b₃ aswell as a central projection 15b₁ ' which projects from the wheel faceand which is jointly operative with the corresponding arcuate groove15b₁ on the wheel 15a₁. Thus, by means of this pair of wheels 15, foldst₂ are formed into the band at the top side of the band, and folds t₃are formed at the bottom side of the band at both sides of the centralaxis X of the band 11. The formation of folds is a preliminary step inthe formation of the top portions 11b₁,11b₂ above the base part 11a ofthe band 11 as will be described below.

FIG. 3C illustrates the next forming stage, in which the forming iscarried out by the pair of wheels 16a₁, 16a₂. The upper wheel 16a₁ is acentral cylindrical support or press wheel. The lower wheel 16a₂comprises, at both sides, conical side faces 16b₁ and 16b₂ placed at anangle of about 45° in relation to the vertical plane. Further, the lowerformer wheel 16a₁ comprises a central groove 16c, whose vertical wallsare connected with the lateral conical side faces 16b₁,16b₂. By means ofthe passage of the band 11 through the space between and into engagementwith wheels 16a₁,16a₂, the rib portions 11a₁,11a₂, . . . are raised fromthe substantially horizontal position as shown in FIG. 3B.

FIG. 3D shows a pair of wheels 17 which constitute the fourth formingstage. The upper wheel 17a₁ is a cylindrical support or press wheelhaving a width of about 1 mm, which in the illustrated embodiment issmaller than the width of wheel 16a₁. The lower wheel 17a₂ has a shapesimilar to that of the lower wheel 16a₂ in FIG. 3C, i.e., a groove 17cand connected conical faces 17b₁,17b₂. The relative angle between theconical faces is smaller than the angle in the preceding forming stage,the angle being considered in relation to the vertical plane. Thus, bymeans of the pair of wheels 17a₁,17a₂ as shown in FIG. 3D, the ribs areraised further gradually.

The last forming stage is carried out by means of the former wheels 18shown in FIG. 3E. As is shown in FIG. 3E as well as FIG. 4, the twoupper wheels 18a₁,18a₂ are mounted to revolve on the shafts a₁₁ and a₁₂on branches R₁₀ ' and R₁₀ " of the frame section R₁₀. Sides G₁ and G₂ ofthe upper wheels 18a₁ and 18a₂ are placed one facing the other and at anacute angle α₁ in relation to one another. The tip angles β of the wheeltips M are acute. The lower wheel 18a₃ revolves on the shaft a₁₀ andcomprises a groove U into which the base portion 11a of the band isplaced. In operation, the tips M of the upper pair of wheels 18a₁ and18a₂ are placed against the fold t₃ and raise the needle ribs into theultimate angle while, at the same time, pressing the top portions11b₁,11b₂ placed above the base part 11a into the ultimate positionparallel to the base part 11a.

FIG. 4 is a separate illustration of the former wheels of the formingstage of FIG. 3E showing the apparatus in greater detail. The wheels18a₁ and 18a₂ are mounted on the shafts a₁₁ and a₁₂ which are connectedto the branches R₁₀ ' and R₁₀ " of the frame R₁₀. The roller wheel 18a₃is rotated by means of the shaft a₁₀. The rotating drive is applied tothe shaft a₁₀ from the belt H. The roll 18a₃ comprises the groove Upassing around the roll in its middle area and the wheels 18a₁ and 18a₂comprise faces G₁ and G₂, which are placed at an angle α₁ in relation toone another, which angle is in the range of from about 55° to about 65°.The tip angles β of the wheels 18a₁ and 18a₂ are in the range of fromabout 50° to about 60°.

The examples provided above are not meant to be exclusive. Many othervariations of the present invention would be obvious to those skilled inthe art, and are contemplated to be within the scope of the appendedclaims.

I claim:
 1. An apparatus for manufacturing a needle-rib heat-exchangerconstruction which comprises an elongate tube and a band wound onto saidtube, the band having a central portion and a lateral portion on eachside of said central portion, comprisingcutting means for cutting thelateral portions of the band, a set of former wheels structured andarranged for shaping the cut band to include a bottom part having firstand second longitudinally extending edge regions, top portions formedfrom the lateral portions of the band between adjacent cuts in the band,said top portions formed from the lateral portions of the band betweeneach pair of adjacent cuts being arranged in opposed relationship to arespective one of said first and second edge regions of said bottompart, and needle-shaped ribs formed from the lateral portions of theband between the adjacent cuts in the band, said needle-shaped ribsformed from the lateral portion of the band between each pair ofadjacent cuts projecting from a respective one of said top portions andbeing situated at an angle in relation to one another, first rotationmeans for rotating said former wheels, and second rotation means forrotating the tube and moving the tube in the longitudinal direction, theband being guided against said rotating former wheels and wound onto thetube.
 2. The apparatus of claim 1, wherein said set of former wheelscomprises nip-defining first and second former wheels, said first formerwheel comprising a projection and a recess on both sides of saidprojection, said second former wheel comprising a recess and aprojection on both sides of said recess and having a complementary shapeto said first wheel, the band being passed through said first and secondformer wheel such that folds are formed into the band by the cooperatingprojections and recesses to enable bending of said top portions to facethe respective one of said first and second edge regions of said bottompart.
 3. The apparatus of claim 1, wherein said set of former wheelscomprises nip-defining first and second former wheels, said first formerwheel comprising a groove and opposed conical faces adjoining saidgroove, defining a space therebetween in which the band is passed andarranged at an angle in relation to one another, said second formerwheel comprising a cylindrical press wheel for pressing the band at alocation between said opposed conical faces to form said needle-shapedribs.
 4. The apparatus of claim 1, wherein said set of former wheelscomprises first, second and third former wheels, said first and secondformer wheels each defining a nip with said third former wheel, saidfirst and second former wheels being rotatable and having a tip with anangle of from about 50° to about 60°, each of said tips engaging a foldin the band between one of said top portions and a respective one ofsaid needle-shaped ribs, and said first and second former wheels havingside faces placed at an angle in relation to one another.
 5. Theapparatus of claim 4, wherein said third former wheel comprises a groovereceivable of said bottom part of the band, the angle between said sidefaces of said first and second former wheels being from about 55° toabout 65°.
 6. The apparatus of claim 4, wherein said third former wheelis rotated by said first rotation means.
 7. The apparatus of claim 1,wherein said first rotation means comprise a motor having an outputshaft and a belt coupling said output shaft to at least some of saidformer wheels.
 8. The apparatus of claim 1, wherein said cutting meanscomprise a punching device including a fixed blade and a movable cuttingblade, said movable cutting blade impacting said fixed blade to form thecuts in the lateral portions of the band.
 9. The apparatus of claim 1,further comprising adhesion means for applying an adhesive agent to saidbottom part of the band for causing adhesion of the band to the tube.10. The apparatus of claim 9, wherein said adhesion means comprises agluing device having a glue applicator wheel.
 11. The apparatus of claim1, wherein said second rotation means comprise three rotatable discsbetween which the tube is positioned.
 12. The apparatus of claim 1,wherein said set of former wheels comprises nip-defining first andsecond former wheels, said first former wheel comprising a projectionand a recess on both sides of said projection, said second former wheelcomprising a recess and a projection on both sides of said recess andhaving a complementary shape to said first wheel, the band being passedthrough said first and second former wheel such that folds are formedinto the band by the cooperating projections and recesses to enablebending of said top portions to face the respective one of said firstand second edge regions of said bottom part,nip-defining third andfourth former wheels arranged after said first and second former wheelsin the direction of travel of the band, said third former wheelcomprising a groove and opposed conical faces adjoining said groove,defining a space therebetween in which the band is passed and arrangedat an angle in relation to one another, said fourth former wheelcomprising a cylindrical press wheel for pressing the band at a locationbetween said opposed conical faces of said third former wheel to formsaid needle-shaped ribs, and fifth, sixth and seventh former wheelsarranged after said third and fourth former wheels in the direction oftravel of the band, said fifth and sixth former wheels each defining anip with said seventh former wheel, said fifth and sixth former wheelsbeing rotatable and having a tip with an angle of from about 50° toabout 60°, each of said tips engaging a fold in the band between one ofsaid top portions and a respective one of said needle-shaped ribs, andsaid fifth and sixth former wheels having side faces placed at an anglein relation to one another.
 13. The apparatus of claim 1, wherein atleast some of said former wheels in said set of former wheels arearranged in pairs.
 14. The apparatus of claim 1, wherein said set offormer wheels comprises a first substantially cylindrical former wheelhaving a wave form on an outer peripheral side surface thereof and asecond substantially cylindrical former wheel having a form on an outerperipheral side surface thereof opposite to the wave form on said firstformer wheel, the band being passed between said first and second formerwheels to be provided with folds based on the wave form of said firstformer wheel.
 15. The apparatus of claim 1, wherein said set of formerwheels shape the band such that said top portions are connected to therespective one of said first and second edge regions of said bottompart.